linux-kernel - Re: [PATCH 00/15] trivial: Drop unlikely before IS_ERR(_OR

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Message-ID: <20150731094920.GB11856@linux>
Date:	Fri, 31 Jul 2015 15:19:20 +0530
From:	Viresh Kumar <viresh.kumar@...aro.org>
To:	Vlastimil Babka <vbabka@...e.cz>
Cc:	akpm@...ux-foundation.org, linaro-kernel@...ts.linaro.org,
	linux-kernel@...r.kernel.org, Steven Rostedt <rostedt@...dmis.org>
Subject: Re: [PATCH 00/15] trivial: Drop unlikely before IS_ERR(_OR_NULL)

On 31-07-15, 11:41, Vlastimil Babka wrote:
> [+CC Steven Rostedt]
> 
> Any idea what the compiler does in the case of
> "if (likely(IS_ERR(...)))"? There are apparently such cases in the source.
> 
> does the "likely" somehow override the "unlikely" of IS_ERR, or is
> the resulting code a mess?

Good point. While fixing all the sites, I saw some code like that. Then before
posting the series, I tried to look at what compilers do to such codes and they
generated exactly same code for:

likely(unlikely(x)) and unlikely(x).

So, either those call sites should drop the likely bits or we supply them with
another raw version of the macro :)

Or if my tests were wrong, then please lemme know.

-- 
viresh
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